The present invention relates to a method for supplying fuel to an internal combustion engine which uses fuel of low startability such as kerosene, alcohol or a mixture fuel of alcohol and gasoline.
In the past, to improve the startability of an internal combustion engine, a choke valve or a starting promoting mechanism was provided for an engine type using a carburetor-type fuel supply system. In a spark ignition engine such as a gasoline engine, an injection valve is electronically controlled in the system using a fuel injection valve to increase the supply of fuel during starting.
Although the startability can be maintained at a normal temperature by the above measures, much more time is required when starting an engine at a low external temperature or HC emission is augmented due to the increase of fuel.
Further, when using a fuel of low volatility other than gasoline, it is difficult to start the engine at a normal temperature or a low temperature, even when the above conventional methods are adopted. In the case of fuel containing methanol at 100%, the lowest possible starting temperature is 5.degree. C. For this reason, the startability of an engine running on methanol is improved by mixing gasoline with the methanol to an approximately 15% concentration when starting the engine. However, the lowest possible starting temperature with such a mixture is still limited to -10.degree. C. to -15.degree. C., and thus remains a problem for engine startability in a low temperature environment.